Burner control system



y 1932- J. A. DAHLSTROM I 1,858,265

0 BURNER CONTROL SYSTEM Filed Jan. 18, 1950 4 Sheets-Sheet 1 gnoe'ntoz duo: ncqS May 17, 1932.

J. A. DAHLSTROM BURNER CONTROL SYSTEM Filed Jan. 18', 1930 4 Sheets-Sheet 2 gnuewioz May 17, 1932- J. A; DAHLSTROM BURNER CONTROL SYSTEM Filed Jan. 18. 1930 4 Sheets-Sheet 3 swam 1 601 Jim flJa/I/Jtrom as M M W dumm Patented May 17, 1932 UNITED STATES PATENT OFFICE JOHN ALGER DAHLSTROM, OF BAY VILLAGE, OHIO, ASSIGNOR TO PERFECTION STOVE COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO BURNER CONTROL SYSTEM Application med January 18, 1930. Serial No. 421,634.

This invention relates to an electric control system for burners, the same being designed for use more especially with fuel oil furnace burners, particularly of the character of that shown in the copending application of Lee S. Chadwick, Marc Resek and myself, filed July 27, 1929, Serial No. 381,600.

The primary purpose of the present invention is to provide a thoroughly reliable and eflicient electrical control system for burners that is relatively simple and wherein practically all switches involved in the system may be concentrated into a relatively small space and mounted upon a single panel or like support.

An important object of the invention is to include, as an element of the system, an exceedingly simple control device, devoid of moving parts, and responsive to combustion conditions, located in intimate heat exchanging relation to the zone of combustion so that it may be readily affected by the heat of the flame. This device comprises an electrical resistance element that is variable when t cool and when hot. The resistance element may consist of a substance having either a negative or a positive temperature coefficient, the former becoming more conductive as its temperature rises, while the latter becomes less conductive at elevated temperatures. Glass is an example of the former and iron or nickel of the latter.

In the present preferred embodiments ofthe invention, I employ glass as the electrical resistance element. As previously stated, glass has a negative temperature coefficient, the characteristic of which. it may be ex-- plained, is dependent upon the composition of the glass. At ordinary room temperatures glass is practically an electrical insulator, but at elevated temperatures its resistance de creases rapidly and to such an extent that at the temperatures of combustion it becomes a good electrical conductor. Iron and nickel,

I on the other hand, possess the quality of increasing in resistance as their temperature rises, but even at the high temperatures of combustion they are still conductors of electricity.

My improved control system functions to stop the operation of the burner upon the occurrence of any one of the following conditions: When the temperature of the room or space that is being heated by the burner has attained a predetermined value; when the heating apparatus itself has become excessively hot or the pressure therein dangerously high; when the apparatus has been started in operation and ignition of the fuel has not occurred; when through any cause the flow of fuel ceases and the fire goes out; when the electrical current fails whether momentarily or for a protracted period, ,or when the pilot light or igniterdoes not function.

Turning now to a more detailed description of the invention by reference to the accom panying drawings, wherein illustrative embodiments are shown, Fig. 1 is a diagramshowing the present preferred form of my improved burner control system; Fig. 2 is a view, similar to Fig. 1, showing a slightly modified form of the invention; Fig. 3 is a sectional view of a furnace burner incorporating my control system, certain units of the system being shown in their relation to the burner; Fig. 4: is a sectional side elevation of the so-called furnace resistor that constitutes one of the unitsof my system; Figs. 5 and 6 are sectional details of the respective lines 55 and 66 of Fig. 4; Fig. 7 is a sectional plan, and Fig. 8 is a sectional side elevation of'a modified form of the furnace resistor; Fig. 9 is a sectional plan view of another form of the furnace resistor; Fig. 10 is a section on the line 10-l0 of Fig. 9; Fig. 11 is a plan view, and Fig. 12 is a sectional side elevation of a further modified form of the furnace resistor; Fig. 13 is 2. diagram showing the system adapted to the use of a furnace resistor having a positive temperature coefficient, and Figs. 14 and 15 are details of such a resistor.

Although my control system is applicable to various types of burners, I have elected to illustrate it in connection with an oil burning apparatus in which the oil is hurled in a horizontal spray or sheet outwardly across a hearth toward an upstanding peripheral wall thereof by means of a fuel delivery cup when the latter is rotated at a relatively high rate of speed by means of an electric motor. The particular burner herein d1s closed is that'constituting the subject matter of the above mentioned application and, as shown in Fig, 3 hereof, it consists of a cup 1 that is supported for rotation by the vertically disposed shaft of an electric motor 2. The cup has 21 depending sleeve 3 which dips into an oil reservoir 4 that is supplied with oil, to a given height, through a pipe 5 equipped with a valve 6. The sleeve 3 dlps into the body of oil in the reservoir 4 and as the cup spins the oil is caused to travel upwardly along said sleeve and through open ings 7 into the interior of the cup where it ascends the wall of the cup and is hurled from the rim thereof across the hearth 10. Air is drawn upwardly about the cup by a fan 11 and is thrown outwardly with the oil and the resultant mixture is ignited by the flame of a pilot burner 12 which, in the present instance, is a gas burner. The oil that travels ,up' the outer side of the sleeve 3 is returned the reservoir by a deflector 13.

The valve 6 is a self closing valve. and is adapted to be opened and held in such condition by electromagnetic means which, in the present instance, is a solenoid designated 15.

Shown as supported in the zone of combustion, as by the peripheral wall of the hearth 10, is what I'have termed the furnace resistor that is designated generally by the reference numeral 16. As best shown in Figs. 4, 5 and 6, the form of furnace resistor disclosed in Fig. 4 consists of two electrodes designated generally by the numerals 17 and 18, the former being in the nature of a cup that is carried by and electrically con- 'nected to an L-shaped bracket 19 whose body portion is arranged above the plane of and parallel with the electrode 18. -The outerends of the parts 18 and 19 are attached together by a block 20 of lava or other insulating material and they carry binding posts 21 and 22, respectively. The downwardly extended inner end of the electrode 18 dips into the cup that constitutes the electrode 17 and is spaced from the walls thereof by a body of glass 23. This body of glass is confined between a bed 24 of lava or the like and a covering 25 of suitable cement. Under ordinary temperatures the electrodes are effectively insulated from each other, but when the glass 23 is raised in temperature to about 1400 F. or above, its conductivity is so increased that the electrodes of the resistor are in practically perfect electrical connection. The metallic parts of this form of furnace resistor are preferably made of sheet metal of a suitable quality, the cup that forms the electrode 17 being constructed of two identical die formed sections that are welded together at their ends and the cup is similarly connected to the depending branch of the bracket 19. This makes a very simple and chea construction and one that is very dura le and capable of withstanding the hlgh temperatures of combustion.

As shown in Figs. 1 and 2, the electrical control system includes, besides the motor 2, solenoid 15 and furnace resistor 16, a transformer 30, a room thermostat 31, a safety switch 32, a so-called furnace switch 33, a main switch 34, and an electromagnetic means 35 for closing the main switch and retaining it closed.

The room thermostat 31 may be of any approved type of thermostatic switch that is adapted to the purpose, and the same is located in the room or space whose temperature is to be controlled. It may consist of a bi-metallic strip 36 which, when affected by a rise in temperature to a predetermined height, will swing into engagement with the contact point 37 The safety switch 32 is adapted to be held closed by a thermostatic element 38 arranged in proximity to an electric heater 40. When the thermostatic element is warped in the direction indicated by the arrow by a rise in temperature of the heater 40 to a predetermined degree, it will release the member 41 of the safety switch, which is biased to open, and permit said member to withdraw from the contact point 42. The switch'member 41 remains in released condition until reset by the manual operation of a button 43 or the like. The member 44 of the furnace switch 33 is adapted to be moved away from a contact point 45 by a pressure device 46 which may consist of a diaphragm 47 within a casing 48. The interior of this casing is adapted to communicate through a pipe 49 with the steam space of the boiler (if the system is used in conjunction with a steam or vapor heating system) or (if otherwise) with a thermostatic means, such as a bulb of mercury or the like, subjected to the heat of the furnace, so that m case the pressure becomes too high or the temperature of the furnace exceeds a safe degree it will distend the diaphragm and, through the intervention of a rod 50, open the switch 33.

The line from which current is derived for operating the system is represented by the conductors and 56 which are connected with the primary winding 57 of the transformer 30. Incidentally the line is shown as including a switch 58. A conductor 59 leads from conductor 55 through the main switch 34 to the motor 2, while a conductor 60 connects the other side of the motor with the conductor 56. Arranged in parallel with the motor, through conductors 61 and 62, is the winding of the solenoid 15 of the oil valve 6.

The foregoing may be considered the main circuit and it may be of the usual 110 volts. I will now describe in connection with the description of the operation of the apparatus the control circuit which includes the second- Lssaaee ary winding of the transformer 36. Assuming that the safety switch 32 and the furnace switch 33 are closed, and that the temperature affecting the roomthermostat 31 is such that the element 36 is in engagement with the contact point 37, current will flow from the secondary winding of the transformer through a conductor 65, the element 36 ofthe thermostat 31, conductor 66, safety switch 32, conductor 6'? furnace switch 33, conductor 68, the winding of the electromagnetic means and conductor 69 to the other end of the secondary winding.

"At the same time a certain amount of the current will flow through a conductor 70, that is shown as including an adjustable resistance 71, and conductor 72, that includes the heater 40, to the previously mentioned conductor 69 and thence back to the secondary winding of the transformer. Another conductor 73 leads from the conductor 70 through the furnace resistor 16 to the conductor 69, but, when the furnace resistor is cool, no currentat least no appreciable amount of current-will flow through the furnace resistor because, as previously explained, the electrodes 17 and 18 of the resistor are effectively insulated from each other by the body of glass 23.

Under conditions now prevailing current is flowing through the winding of the electromagnetic means 35 and through'the heater 40. Upon the energization of the electromagnetic means 35, the main switch 34: is closed which, in turn, energizes the motor 2 and the winding of the solenoid 15. Upon the occurrence of these things the oil valve is opened to throw the reservoir 4 of the burner into communication with a source of supply (not shown), and the motor will start spinning the cup 1. As soon as the motor is well under Way the mixture of oil and air that 1s hurled outwardly by the cup 1 and fan 11 will be ignited by the flame of the pilot burner 12 and combustion will start. Shortly thereafter the temperature of the furnace resistor 16 will be raised to the necessary point to convert the body of glass 23 into' an efi'ective conductor whereupon current will flow through the conductor 73 more free'-' ly than it will through the circuits including the winding of the electromagnetic means 35 and the heater 40. Consequently the strength of the electromagnetic means will be considerably weakened, but yet it'will possess sufiicientstrength to retain the main switch 34 closed; and the heater 40 will be unable under its present supply. of current to sufliciently warp the thermostatic element 38 to cause it to release the member 41 of the safety switch 32. The current flowing under these conditions through the winding of the electromagnetic means 35 is not sufficient to cause said means to close the main switch if the same should be opened through any cause.

prolonged period; or if the furnace should ecome overheated, or the pressure in the boiler excessive, and open the furnace switch 33, or if the room thermostat 31 opens the circuit, through its normal operation, the supply of current to the motor would cease and the apparatus stop working. It will be evident, also, that if the current failure were only for a moment, giving the furnace resistor 16 insuiiicient time to cool down to something near normal temperature, the apparatus would not start operating again upon resumption of current flow because there would not be enough current flowing through the winding of the electromagnetic means 35 to close the main switch. This is important as otherwise oil might be hurled onto a hot hearth and cause an explosion, it being understood that the time required for the furnace resistor tolose its high conductivity is enough to allow the burner parts to cool down. This possibility of an explosion is caused by the fact that the oil being sprayed on the hot hearth is vaporized very quickly and a large volume is built up in the combustion chamber before the pilot can ignite it. Although this is a rare possibility, it should be safeguarded against.

In case the operation of the apparatus is started as already described and, through some cause, the pilot burner is out, the fur nace resistor 16 will remain cool and current will only flow through the circuits including the winding of the electromagnetic means 35 and the heater 40. Under these conditions enough current will flow through the heater to elevate the temperature, within The same thing will occur of combustion and a cooling down of the furnace resistor 16.

The resistance 71 is preferably made adjustable so that the current flow through therespective circuits including the furnace resistor 16 and the winding of the electromagnetic means 35 may be properly ba'lanced.

The only difference in the embodiment shown in Fig. 2 from that disclosed in Fig.

1 is that in the case of Fig. 2 the furnace resistor 16 and the heater 40 are in independent shunt circuits represented,respectively, by the conductors 73 and 72. The shunt circuit of the furnace resistor 16 includes also an adjustable resistance 71". The layout of Fig. 2 contemplates the use of a low regulation type of transformer so that as current flows through the furnace resistor 16 a bigger load is put on the transformer thereby reducing its secondary voltage. This reduction so weakens the electromagnetic means 35. that it serves only to retain the main switch 34 closed, it being incapable in its weakened condition to close the switch in case it should be opened while the furnace resistor is hot. The current flowing through the heater 40 is also weakened under the conditions described that is, while the furnace resistor 16 is hot-and to such an extent that it will not cause sufiicient warping of the thermostatic element 38 to release the member 41 of the safety switch 32. In this case,

therefore, the adjustable resistor 71 not only provides for the attainment of the desired current variation between the circuits including the furnace resistor and the winding of the electromagnetic means 35 but also enables the current flow through the heater 40 to be regulated and controlled to the proper deree. g The furnace resistor illustrated in Figs.

7 and 8 consists of a stem 75 of suitable refractory insulating material having two longitudinal, parallel bores through which wires or conductors 76 are extended and a cup 77, of lava or the like, is supported at the inner end of the stem by said wires. A body 78 of glass occupies the cup and-is mold ed about the portions of the wires or conductors 76 that extend across the interior of the cup.

The form of furnace resistor illustrated in Figs. 9 and 10 consists of-a stem 80 of refractory material through parallel longitudinal bores of which wires 81 are extended into a well 82 that is formed in the outer end of a head 83 of lava or the like that is applied to the forward end of the stem. Said well, wherein the ends of the wires 81 are exposed, is filled with glass that is sealed therein by a suitable closure 84, such as a deposit of cement.

In Figs. 11 and 12 is illustrated a form of furnace resistor consisting of two L-shaped wires 85. The right angular end portions of these wires project upwardly within the bore of a porcelain sleeve 86 that contains a body 87 of glass.

The diagram of Fig. 13 shows the invention adapted to the use of a furnace resistor having a positive temperature coeflicient. Such a resistor, designated generally by the reference character 16 and shown in eleva tion in Fig. 14. and in section in Fig. 15, may consist of a frame or support 90 of lava or other refractory insulating material, and a coil 91 of nickel wire wound thereon. In

Fig. 13, the parts of the system other than those just mentioned are designated by the same reference characters as are applied to -mented by the exponent b.

In describing the operation of the form now under consideration it will be assumed that the switch constituted of the room'thermostat 31 is closed by a drop in temperature and a demand for more heat. Current will flow from the secondary winding of the transformer through conductor 65, thermostat 31, conductor 66, furnace switch 33, conductor 68, furnace resistor 16", conductor designated 68", the winding of the electromagnetic device 35, conductor 69", heater 40, conductor 70*, safety switch 32, and conductor 71 to the secondary of the transformer.

Enough current will pass throu h the furnace resistor 16 when it is cold and its conductivity high to create within the electromagnetic device suflicient force to close the switch 34. Thereupon the oil valve will be opened and the motor started, as in the previously described cases.

After the furnace resistor becomes heated to the temperature of combustion, its conductivity is so reduced that only sufficient current is passed to impart to the electromagnetic device enough strength to hold switch 34 closed. Therefore, should the switch become opened, as by a momentary failure of the current, the system could not recycle until the burner parts and furnace resistor have had time to cool down, thereby avoiding any possibility of an explosion.

40 to raise its temperature to that required to release safety switch 32, but upon ignition failure and the resistor remaining cool,

or a going out of the burner from any cause and the resistor cooling, the current flow through it and through the heater will be sufiicient to cause the latter to attain that predetermined degree of temperature requisite to the release of the safety switch member 41 by the warping of the thermostatic element 38.

Having thus described my invention, what I claim is 1. In a burner control system, in combination with electrical means for delivering fuel to the zone of combustion, means for ignit ing the fuel, a circuit including said electrical means, a switch in said circuit, an electromagnetic device for closing said switch and for holding it closed, a furnace resistor whose electrical resistance is responsive to combustion conditions and becomes less as the heat increases, said resistor being arranged in heat exchanging relation to the zone of combustion, and a circuit arrangement including said resistor and said electromagnetic device, the resistor serving when heated torob the electromagnetic device of current thereby to render said device incapable of closing the aforesaid switch but is of sufiicient strength to hold said switch closed.

2. In combination, a switch biased toward open position, electromagnetic means for closing said switch and for retaining it closed, a device adapted to be subjected to a source of heat and whose electrical resistance is variable when hot and cold, and a circuit arrangement including said electromagnetic means and said device, said device when hot serving by reason of its variable resistance to reduce the current delivered to the electromagnetic means thereby to render said means capable only of holding the switch closed and incapable of closing the switch, if opened. I 3., In combination, an oil burner, and a control system therefor including an electric motor, a switch for governing the operation of the same, a relay for closing said switch, a safety switch which, when opened, stops the operation of the burner, and adevice whose electrical resistance varies with its temperature and is so arranged as to be responsive to the combustion conditions of the burner, the same being so electrically connected with the safety switch and relay that, when hot,

' and by reason of its variable resistance it roles the relay of current and thereby renders it incapable of closing the motor switch, and, when cold, causes the maximum current fiow to the safet switch thereby to efiect the opening thereoi 4. In combination, an oil burner, and a control system therefor including an electric motor, a switch for governing the operation of the same, a relay for closing said switch, and a device whose electrical resistance varies with its temperature and is so arranged as to be responsive to the combustion conditions of the burner, the same being so electrically connected with the relay that, when hot, and by reason of its variable resistance it so reduces the amount of current delivered tocthe relay as to render the latter incapable of closing the motor switch.

5. In a burner control system, in combina- I tion with electrical means for delivering fuel to the zone of combustion, means for ignit-i ing the fuel, a main circuit including the fuel delivering means, a switch in the main circuit biased toward open position, electromagnetic means for closing said switch and for retaining it closed, a control circuit including said electromagnetic means, a source of current therefor, a shunt circuit within the control circuit between the source of current and the aforesaid electromagnetic means, and an electrical resistance in the shunt circuit in heat exchanging relation to the zone of combustion and variable when the fuel is burning and not burning, said electrical resistance when heated by the burning fuel serving by reason of its increased conductivity to pass suflicient current to so weaken that delivered to the aforesaid electromagnetic means as to rendersaid means capable only of retaining the switch in the main circuit closed but incapable of closing it in case it opens.

6. In a burner control system, in combination with electrical means for delivering fuel to the zone of combustion, means for igniting the fuel, a main circuit including the fuel delivering means, a switch in the main circuit biased toward open position, electromagnetic means for closing said switch and for retaining it closed, a control circuit including said electromagnetic means, a source of current therefor, a thermostatically controlled switch in said circuit, a double branch shunt circuit within the control circuit between the source of current and the aforesaid electromagnetic means, an electric heater in one branch of the shunt circuit for efiecting the opening of the thermostatic switch upon the attainment of a predetermined temperature, and an electrical resistance in the other branch of the shunt circuit in heat exchanging relation to the zone of combustion and variable when the fuel is burning and not burning, said electrical resistance when heated by the burning fuel serving to pass suficient current to so weaken that delivered to the aforesaid electromagnetic means as to render said means capableonly of retaining the switch in the main circuit closed but incapable of closing it in case it opens.

7 in a burner control system, in combination with electrical means for delivering fuel to the zone of combustion, means for igniting the fuel, a transformer, a main circuit ineluding the fuel delivering means, a circuit in parallel with the main circuit including the primary winding of the transformer, a switch in the main circuit that is biased toward open position, electromagnetic means for closing said switch and for retaining it closed, a control circuit including said electromagnetic means and the secondary winding of the transformer, a shunt circuit in the control circuit between the electromagnetic means and the secondary winding of the transformer, and an electrical resistance in the shunt circuit arranged in heat exchanging relation to the zone of combustion and variable when the fuel is burning and not burning.

8. In a burner control system, in combination with electrical means for delivering fuel to the zone of combustion, means for igniting the fuel, a transformer, a main circuit including the fuel delivering means, a circuit in parallel with the main circuit including the primary winding of the transformer, a switch in the main circuit that is biased toward open position, electromagnetic means for closing said switch and for retaining it closed, a control circuit including said electromagnetic means and the secondary winding of the transformer, a double branch shunt circuit in the control circuit between the electromagnetic means and the secondary winding of the transformer, a

thermostatically controlled switch in the control circuit, an electric heater in one branch of the shunt circuit for effecting the opening of the thermostatic switch upon the attainment of a predetermined temperature, and

an electrical resistance in the other branch of the shunt circuit arranged in heat ex- 10 changing relation to the zone of combustion and variable when the fuel is burning and not burning.

9. In a burner control system, in combination with electrical means for delivering fuel to the zone of combustion, means for igniting the fuel, a transformer, a main circuit mcluding the fuel delivering means, a circuit in parallel with the main circuit including the rimary winding of the transformer, a switch in the main circuit that is biased toward open position, electromagnetic means for closing said switch and for retaining it closed, a control circuit including said electromagnetic means and the secondary winding of the transformer, a double branch shunt circuit in the control circuit between the electromagnetic means and the secondary winding of the, transformer, a thermostatically controlled switch in the control circuit, an electric heater 0 in one branch of the shunt circuit for effecting the opening of the thermostatic switch upon the attainment of a predetermined temperature, an electrical resistance in the other branch of the shunt circuit arranged in heat exchanging relation to the zone of combustion and variable when the fuel is burning and not burning, and an adjustable resistance in the shunt circuit.

In testimony whereof, I hereunto afiix my signature.

JOHN ALGER DAHLSTROM. 

